CAEBON DIOXIDE AT DIFFERENT TEMPERATURES. 203 



DETAILS OF THE APPARATUS. 



(4) The Continuous Flow Electrical Calorimeter. The calorimeter is represented 

 diagrammatically in fig. 1. The tube AB, which may be termed the calorimeter 

 proper, consisted of a glass tube about 60 cm. long, the space containing the platinum 

 thermometers and heating coil being surrounded by a glass jacket/. The calorimeter 

 proper was fixed by rubber corks C, D, E, into a double-walled vessel, 44 cm. long 

 and 5 cm. internal diameter, which was continued into a double-walled tube FG, 

 packed with tightly-fitting discs of copper gauze. The tube FG formed the heater 

 in which the gas attained the desired temperature. The whole double-walled vessel 

 thus consisted of two L-shaped vessels, one inside the other, the ends of the annular 

 spaces between the double walls being closed with tightly-fitting brass rings soldered 

 in. The space between the double walls was provided with an inlet (i) and an outlet 

 (o), so that water or steam could be passed round the apparatus for the purpose of 

 keeping it at a constant temperature. The gas under investigation entered by the 

 tube m, passed through the tightly-packed gauze in GF, where it took up the 

 required temperature, and entered the space round the calorimeter proper ; it next 

 passed through the tube n into the calorimeter proper, and finally emerged by the 

 tube p. The ends of AB were closed by the rubber corks through which the 

 platinum thermometers and heating coil leads passed. 



The above method of heating the gas was found to be most efficient ; a thermometer 

 placed in the exit end of the calorimeter proper recorded 99'9 C., while the same 

 thermometer placed in the steam recorded 100 C. The essential requirement was 

 not that the temperature of the gas should be exactly equal to that of the steam, 

 but that it should remain constant, and this was found to be the case to a surprisingly 

 high order of accuracy, the temperature remaining steady often to 0- 01 C. for two 

 or three hours, allowance being made for fluctuations in atmospheric pressure. The 

 function of the cork D was to prevent the gas becoming cooled by impinging on the 

 cork E, which was in direct contact with the atmosphere. A slight cooling effect, 

 due to the gas impinging on C, was of little consequence, since it became warmed 

 again in its passage down the jacket of the calorimeter proper, and it was the 

 temperature of this gas which determined the temperature of the jacket j. All 

 that was essential was that the gas should enter the calorimeter proper at the 

 temperature of the jacket j. The parts of the leads which were contained in that 

 portion of the calorimeter proper, which projected outside the jacket, were lagged 

 with cotton wool in order to reduce the temperature gradient in them, and 

 consequently the conduction of heat from the gas. 



(5) The Platinum Thermometers and Heating Coil. The platinum thermometers 

 and heating coil were wound on three serrated mica frames. The heating coil leads 

 were four in number, two for carrying the current, and two for connection to the 

 potentiometer. Each current lead was connected to its potential lead by a piece 



2 D 2 



